1. Field of the Invention
The present invention relates to the field of liquid crystal displaying, and in particular to a combined backplane and a backlight module using the combined backplane.
2. The Related Arts
Liquid crystal display (LCD) has a variety of advantages, such as compact device size, low power consumption, and being free of radiation, and is thus widely used. Most of the LCDs that are currently available in the market are backlighting LCDs, which comprise a liquid crystal display panel and a backlight module. The working principle of the liquid crystal display panel is that liquid crystal molecules interposed between two parallel glass plates and a plurality of vertical and horizontal fine electrical wires is arranged between the two glass plates, whereby the liquid crystal molecules are controlled to change direction by application of electricity to refract light emitting from the backlight module for generating images. Since the liquid crystal display panel itself does not emit light, light must be provided by the backlight module in order to generate images. Thus, the backlight module is one of the key components of an LCD. The backlight module can be classified as two types, namely side-edge backlight module and direct backlight module, according to the position where light gets incident. The direct backlight module arranges a light source, such as a cold cathode fluorescent lamp (CCFL) or a light-emitting diode (LED) at the back side of the liquid crystal display panel to form a planar light source to directly provide lighting to the liquid crystal display panel. The side-edge backlight module arranged a backlight source, such as an LED light bar based light source, at an edge of a back panel that is located rearward of one side of the liquid crystal display panel. The LED backlight source emits light that enters a light guide plate through a light incident face of the light guide plate and is projected out through a light exit face after being reflected and diffused to thereby form a planar light source to be provided to the liquid crystal display panel.
A conventional backlight module generally comprises a backplane, a light guide board, a backlight source, and optic films. The backplane is generally made of a single material, which is for example aluminum plate, steel plate, or plastic plate. If the backplane is completely made of a steel plate, then a heat dissipation element is additionally used. This increases the costs. If the backplane is completely made of an aluminum plate, then no additional heat dissipation element is necessary. Although aluminum has better thermal conductivity than steel, yet the backplane uses only a portion thereof to effect heat dissipation, while the remaining portion provides a function of support rather than dissipation of heat. This is adverse to expenditure control and support and retention of liquid crystal module.
The conventional ways of mounting a backlight source to a backplane includes thermally conductive adhesive tapes or bolts. A backlight source can be fixed by thermally conductive adhesive tapes to a backplane, but the thermally conductive adhesive tapes have great thermal resistance and has a thermal conductivity of around 0.9-6 W/K*m. On the other hand, aluminum shows a thermal conductivity up to 137 W/K*m. Although the thermal conductivities of the backlight source and the backplane are great, yet the thermally conductive adhesive tapes have relatively low thermal conductivity, so that the heat generated by the backlight source cannot be efficiently removed. For the case where the backlight source is fixed to the backplane by bolts, air layers are commonly present between the backlight source and the backplane at locations where no bolt is applied. Since the thermal conductivity of air is even poorer, the thermal resistance at the contact surface is increased, making the overall heat dissipation poor.